Pretest probability assessment plays an important role in the evaluation of pulmonary embolism (PE) in the emergency department (ED). Current methods of pretest probability assessment produce categories of risk that tend to over fit individual patients. The hypothesis of this work is that the pretest probability of PE can be accurately estimated by computerized matching of symptoms, signs and risk factors from an individual patient under evaluation in the ED to a large reference database of patients previously evaluated for PE. To accumulate a large database from ED patients undergoing objective testing for PE, a clinician-friendly method for prospective data collection in the ED is needed. Phase I will develop this method as an electronic data form to collect clinical data using personal digital assistants (PDAs) in conjunction with a website to download entered data. The first specific aim is to develop the electronic data form (e-form) for use on PDAs to facilitate the prospective recording of 62 fields of clinical data rapidly and prior to knowledge of the results of pulmonary imaging while the patient is in the ED. The second specific aim is to create the website for clinicians to download and install the e-form on their PDAs and to upload completed e-forms for permanent storage of clinical data. The website will encrypt patient identifier information but will allow the input of information obtained at follow-up. The third specific aim is to pilot test the e-form and website mechanism on 40 emergency physicians studying approximately 150 patients undergoing evaluation for PE at the Research Institution. This project will be accomplished through collaboration between the applicant, BreathQuant Medical Systems Inc and Carolinas Medical Center (the Research Institution and employer of the PI), with technical support and advice from iReadyWorld, a software and website development firm, located in Charlotte, NC. The long-term significance of this project includes: 1. Development of a method to simplify the collection of a large volume of data from a large number of ED patients tested for PE, 2. Phase II will accumulate the database that will serve as substrate for a commercial product that accurately estimates pretest probability for PE. The method and database will also address other questions relevant to public health, including the frequency and results of testing for PE in overcrowded U.S. EDs, the current treatment choices for PE, and the short-term complications and mortality from treated PE.